1. Field of the Invention
The present invention relates to a process or treatment for decontaminating process water, and more particularly relates to a novel process for removing metal pollution from electroplating and etching process water, such as the removal of metal ions commonly used in metal plating, etching and anodizing operations.
2. Brief Description of the Prior Art
As the requirement for environmental control has expanded with the increase in technological advancement and with the widening demand for improved processes and apparatus capable of handling waste products therefrom, the need for improved and safer decontamination treatments of liquids as a waste product has become of increasing importance. A concomitant of this trend is the need for effectively lowering the amounts of metal ions to acceptable standards of regulatory agencies which, while providing the requisite degree of safety, provides a convenient and manageable form of solid product rendered to a state of least environmental risk for storage or disposal. Under the thrust of this expanding requirement, it has become an economic necessity to provide an innovative process and apparatus which both minimizes the possibility of error in the decontamination procedures and reduces overall system complexity.
Particularly, in the field of electroplating and etching procedures, the accumulation of metal ions in the process water has accelerated into a critical problem for contamination and disposal. Treatment technology for removal of metal ions associated with metal plating, electroplating and etching operations is essentially linked to the use of hydroxide or sulfide precipitations. However, under actual operating field conditions, complete removal of metal ions is rarely achieved. Thus, a substantial amount of metal ions remain in the process water, some of which are carcinogenic and/or are toxic to human life, which the regulatory authorities find objectionable. There have been several new and emerging technologies to lower the levels of metal ions in the process water; however, such prior attempts have not satisfied or reached acceptable decontamination levels and questions of storage and disposal are still in existence.
Therefore, there is a growing concern, as well as a real need to improve the technology that effectively removes metal ions from the process water. An equally important concern is the fate or ultimate disposal of the resultant sludge or final sludge product.